The present invention relates to a seatbelt retractor for use in a passenger car, etc., in order to ensure the safety of vehicle occupants.
A seatbelt retractor must be installed in order to secure the safety of a vehicle occupant upon an accident such as collision, and various types thereof have been developed. An example of the simplest structure thereof is shown in FIG. 16.
A spring cover 41, which is a supporter at one side of the seatbelt retractor, is provided with a bearing 41a arranged therein, into which a shaft 42a of a spool 42 is fitted so as to rotate while a force in the retracting direction is applied to the shaft 42a by a spring. A seatbelt is wound around the spool 42.
Inside the spool 42, a concave fitted portion (not shown) is formed, into which one end of a torsion bar 43 is fitted. The other end of the torsion bar 43 is fitted into a concave fitted portion (not shown) formed in a locking base 44. A shaft 44a of the locking base 44 passes through a hole 45a of a lock gear 45 so as to fit into a bearing (not shown) of a retainer 46, which is a supporter on the other side of the seatbelt retractor.
Such a mechanism results in supporting the spool 42 at its rotating shaft by the spring cover 41 and the retainer 46 and rotating the spool 42 so as to retract the seatbelt by means of the spring. The spring cover 41 and the retainer 46 are fixed at both ends of a base frame 48, so that the spool 42 is accommodated within the base frame 48.
In these structural elements, the locking base 44 and the lock gear 45 are rotatable by a predetermined angle, so that the lock gear 45 is urged by a spring 49 relative to the locking base 44 in the direction pulling out or withdrawing the seatbelt so as to approach the limit of the relative rotation.
When the seatbelt is withdrawn in a normal state, since there is no rotational resistance against the lock gear 45, the lock gear 45 can not overcome the urging force of the spring 49. As a result, the lock gear 45 rotates integrally with the locking base 44.
Even when the locking base 44 is rotated in the withdrawing direction as the spool 42 is rotated by the spring force, the lock gear 45 rotates integrally with the locking base 44 because the lock gear 45 is designed to approach the limit of the rotation relative to the locking base 44 in this direction as mentioned above.
When abrupt retraction force to the seatbelt is produced due to a collision or the likes, a flywheel 50 accommodated within the lock gear 45 is displaced by overcoming the urging force of a spring 51, so that the lock gear 45 can not rotate relative to the retainer 46, thus of the seatbelt being stopped.
Then, the rocking base 44 rotates relative to the lock gear 45 against the urging force of the spring 49. A mechanism is constructed such that a pawl 52 accommodated in the locking base 44 is protruded outside by this relative rotation, and a gear of the externally protruded pawl 52 is brought into engagement with a gear section 48a formed in the base frame 48, also stopping the rotation of the locking base 44.
Accordingly, rotation of the torsion bar 43 is also stopped and the spool 42 is allowed to rotate only by an angle corresponding to a twist of the torsion bar 43. Therefore, the spool 42 is thereafter rotated under a tension increasing as the seatbelt is withdrawn. The locking mechanism described above is generally called as xe2x80x9ca locking mechanism by a web sensorxe2x80x9d.
The description above only illustrates an outline of the seatbelt retractor and there are complex mechanisms for use as a mechanism for stopping the rotation of the lock gear 45 by the movement of the flywheel 50 and a mechanism for protruding the pawl 52 outside, for example. However, the seatbelt retractor is known and in common use, so that more detailed description may not be necessary for those skilled in the art, and moreover, it is irrelevant to the principal part of the present invention, so that the more detailed description is omitted.
However, in the conventional seatbelt retractor, since the lock mechanism is operated after the seatbelt is actually withdrawn suddenly, a time lag in operating the lock mechanism may be developed. There is also a problem that when the seatbelt is withdrawn in a state that a motor shaft is connected to the spool, a force for withdrawal or retraction is required and a force for retracting the seatbelt is not sufficient. Furthermore, when the seatbelt is rapidly withdrawn during wearing the seatbelt, the lock mechanism may also be operated. This results in for an occupant feeling uncomfortable or unpleasantness.
The present invention has been made in view of such situations, and it is an object of the present invention to provide a seatbelt retractor which can promptly operate a lock mechanism upon an emergency.
It is another object of the invention to provide a seatbelt retractor which eliminates uncomfortable feeling or unpleasantness to an occupant caused by unnecessary operation of locking mechanism upon wearing the seatbelt without reducing the retractor efficiency.
In order to solve the problems described above, a seatbelt retractor has a mechanism for retracting a seatbelt by a motor. The seatbelt retractor comprises a switching mechanism for switching on and off a power transmission route between the motor and a spool around which the seatbelt is wound, in which the power transmission route between the motor and the spool is connected only when the motor rotates in the retracting direction, and a ratchet mechanism in which, during operation, the spool rotates only in the seatbelt-retraction direction and during non-operation, the spool is allowed to rotate in any directions (the first aspect).
In the mechanism, when the motor does not rotate in the retracting direction, the power transmission route between the motor and the spool is not connected by the switching mechanism of the power transmission route. Therefore, the mechanical power transmission between the motor and the spool is not performed. At this time, by turning the ratchet mechanism off, the spool can freely rotate without any load applied thereto by the motor and rotational disturbance by the ratchet mechanism. Accordingly, the seatbelt is retracted only by a retracting force due to the spring torque, so that a vehicle occupant will not feel uncomfortable.
When a collision detecting device attached to a vehicle detects abrupt braking, a large acceleration, and so forth so as to determine that there is a possible collision, the device sends a signal to the motor to retract the seatbelt simultaneously with putting the ratchet mechanism into an operating state. Then, the power transmission route between the motor and the spool is connected by the switching mechanism of the power transmission route, so that the spool is rotated by the winding force of the motor so as to retract the seatbelt. Due to operation of the ratchet mechanism, the spool rotates only in the seatbelt-retraction direction but not in the seatbelt-withdrawing direction, enabling a vehicle occupant to be securely restrained to a seat.
A seatbelt retractor can be equipped with a switching mechanism of a power transmission route which is driven by a rotational force of a motor in the seatbelt-retraction direction so as to connect the power transmission route between the motor and the spool having the seatbelt wound therearound.
In the first aspect, turning on (connection) and off (disconnection) the power transmission route is operated by the rotational torque of the motor, so that an actuator driven by the other power for operating the switching mechanism of the power transmission route, such as an electromagnetic solenoid, is not required. Therefore, the switching mechanism of the power transmission route cab be comprised of the smaller number of parts, and a simplified structure and cost reduction can be achieved.
In the second aspect, in a seatbelt retractor of the first embodiment, the power transmission route is provided with a power transmission gear mechanism while the switching mechanism of the power transmission route has a rotatable control lever for controlling operation of the switching mechanism of the power transmission route, so that the switching mechanism of the power transmission route is operated by rotation of the control lever due to the rotational torque of the motor so as to establish the power transmission route in a connected state.
In the second aspect, when the motor rotates in the retracting direction, the control lever is rotated by the motor torque so as to operate the switching mechanism of the power transmission route to enable the power transmission between the motor and the spool. When the motor does not rotate, the control lever is located at its initial position so as not to operate the switching mechanism of the power transmission route, so that the power transmission between the motor and the spool is disconnected and the spool can rotate freely. Therefore, the turning on and off the power transmission between the motor and the spool can be performed by a simplified structure.
As the third aspect of the invention, the power transmission route is provided with a mechanism that reduces rotation of the motor in speed from the power transmission gear mechanism so as to transmit it to the spool. The reduction mechanism comprises a sun gear, a ring-shaped internal gear having ratchet teeth at the external periphery and internal teeth on the internal circumference, planetary gears engaging the sun gear and the internal gear, a carrier for supporting the planetary gears simultaneously with transmitting revolution of the planetary gears to the spool, and a reduction gear disposed to rotate integrally with the sun gear, in which rotation of the motor is input from the power transmission gear mechanism.
The switching mechanism of the power transmission route further comprises a retaining lever that can rotate between a position disengaged from ratchet teeth and a position engaged with the ratchet teeth. In a normal state in which the control lever does not rotate, the retaining lever is put at the non-engaging position so as to allow the internal gear to rotate, and when the control lever rotates, the retaining lever is put at the engaging position so as to prevent the internal gear from rotation by engagement between the ratchet teeth and the retaining lever. When the internal gear can rotate, the power transmission route is established to be in a disconnected state, and when the internal gear is prevented from rotation, the power transmission route is established to be in a connected state.
In the third aspect, when the retaining lever is not engaged with the ratchet teeth, the internal gear can rotate without substantial load. When the motor rotates in this state, the reduction gear and the sun gear are rotated. Then, because the internal gear can rotate without substantial load while revolution of the planetary gears is subjected to the load of the spool, the planetary gears do not revolve and each planetary gear rotates on its axis so as to rotate the internal gear. Therefore, the motor power can not be transmitted to the spool.
When the spool rotates in this state, although the planetary gears revolve, the sun gear is subjected to the motor load while the internal gear has no load, so that the planetary gears revolve while rotating the internal gear but not rotating the sun gear. The power transmission between the spool and the motor is disconnected, so that the retraction and withdrawal of the seatbelt can be freely performed without receiving the motor load.
When the retaining lever is engaged with the ratchet teeth, the internal gear is prevented from rotating. When the motor rotates in this state, the reduction gear and the sun gear are rotated. Then, since the internal gear can not rotate, the planetary gears are rotated on their axes by the sun gear simultaneously with receiving a revolving force from the internal gear so as to revolve. Therefore, the spool connected to the internal gear rotates by receiving a driving force. At this time, when the spool rotates, the sun gear is also subjected to the driving force by revolving of the internal gear, so that the motor receives the driving force. Thus, the power transmission route between the spool and the motor is connected.
As the fourth aspect of the invention, the power transmission route is provided with a reduction mechanism for reducing rotation of the motor in a speed from the power transmission gear mechanism so as to transmit it to the spool. The reduction mechanism comprises a sun gear, a ring-shaped internal rotation gear having ratchet teeth at the external circumference and internal teeth on the internal circumference, planetary gears engaging the sun gear and the internal gear, a carrier for supporting the planetary gears simultaneously with transmitting rotation of the motor to the spool, and a reduction gear disposed to rotate integrally with the sun gear and to transmit the rotation thereof to the spool.
The switching mechanism of the power transmission route further comprises a retaining lever that can rotate between a position disengageable from the ratchet teeth and a position engageable with the ratchet teeth. In a normal state in which the control lever does not rotate, the retaining lever is put at the non-engaging position so as to allow the internal gear to rotate, and when the control lever rotates, the retaining lever is put at the engaging position so as to prevent the internal gear from rotation by engagement between the ratchet teeth and the retaining lever. When the internal gear can rotate, the power transmission route is established to be in a disconnected state, and when the internal gear is prevented from rotation, the power transmission route is established to be in a connected state.
The fourth aspect is different from the third aspect only in that the sun gear and the reduction gear are connected to the spool side and the planetary gear side is connected to the motor side, so that operation thereof is the same as that of the third embodiment. Therefore, the operation and advantages similar to those of the third embodiment can be achieved.
As another preferred aspect (the fifth aspect) of the invention, the abovementioned ratchet mechanism comprises a ratchet gear having saw-blade teeth at the external circumference and directly connected to a rotational shaft of the seatbelt retractor or engaged with a gear directly connected to the rotational shaft, a pawl arranged to be engageable with the saw-blade teeth, a lever for driving the pawl so as to engage with and disengage from the saw-blade teeth, and a rotational body for driving the lever via a torque limiter, wherein the rotational body is driven by the motor.
As the fifth aspect, the motor is located at a normal position where the pawl is not engaged with saw-blade teeth of the ratchet gear. Upon receiving a collision predicting signal, the motor rotates, and a rotational body is rotated. The lever is driven so as to drive the pawl to a position engaging the saw-blade teeth of the ratchet gear. Therefore, the pawl and the ratchet gear form the ratchet mechanism, so that the ratchet gear can rotate in the seatbelt-retraction direction but it can not rotate in the withdrawing direction. Accordingly, the rotational shaft of the seatbelt retractor directly connected to the ratchet gear or connected thereto via a gear is also prevented from rotating in the withdrawing direction.
In this case, although the motor continues to rotate, because the torque limiter is arranged between the rotational body and the lever, a force for pushing the pawl by the ratchet gear is limited to a force determined by the torque limiter, so that the rotation of the ratchet gear in the direction retracting the seatbelt can not be prevented and the lever, etc. can not be damaged.
As the sixth aspect of the invention, the ratchet mechanism comprises a ratchet gear having saw-blade teeth at the external circumference that are directly connected to a rotational shaft of the seatbelt retractor or is engaged with a gear directly connected to a rotational shaft, a pawl which is arranged to be engageable with the saw-blade teeth and which rotates about a rotational pin arranged in a fixed part of the seatbelt retractor, and a driving mechanism for driving the pawl so as to engage with and disengage from the saw-blade teeth via an elastic body.
In the sixth aspect, a pawl driven by a driving device is located at a normal position such that the pawl is not engaged with the saw-blade teeth of the ratchet gear. Upon receiving a collision predicting signal, the driving device operates, and the lever is driven via an elastic body so as to rotate the pawl to a position engaging the saw-blade teeth of the ratchet gear. Therefore, the pawl and the ratchet gear form a ratchet mechanism, so that the ratchet gear can rotate in the direction retracting the seatbelt while can not rotate in the withdrawing direction. Accordingly, the rotational shaft of the seatbelt retractor directly connected to the ratchet gear or connected thereto via a gear is also prevented from rotating in the withdrawing direction.
In this case, because the elastic body is arranged between the driving device and the lever, a force of the ratchet gear for rotating in the direction retracting the seatbelt is absorbed by the elastic body so as not to prevent the rotation.
As another preferred aspect (the seventh aspect) of the invention, the abovementioned ratchet mechanism comprises a ratchet gear having saw-blade teeth at the external circumference that are directly connected to the rotational shaft of the seatbelt retractor or are engaged with a gear directly connected to the rotational shaft, a pawl that is arranged to be engageable with saw-blade teeth by rotation and has a pin fitted into a slotted hole formed on a fixed part of the seatbelt retractor, and a ratchet lever that is arranged to be connected to a reciprocation driving unit and has a rotational pivot of the pawl.
When the reciprocation driving unit is located at a first position, the pawl rotational pivot of the ratchet lever is located at a first position while the shaft of the pawl is located at one end of the slotted hole, so that the pawl is positioned apart from the ratchet gear. When the reciprocation driving unit is located at a second position, the pawl rotational pivot of the ratchet lever is located at a second position, so that the pawl is located at an engageable position with the ratchet gear. When the spool is rotated in the withdrawing direction at this state, the pawl rotates about the pawl rotational pivot so as to be stopped by abutment of the pin against the one end of the slotted hole, so that rotation of the ratchet gear is stopped. When the spool is rotated in the retracting direction, the pawl rotates about the pawl rotational pivot in the direction opposite to the aforementioned direction, so that the rotation of the ratchet gear is allowed by positioning of the pin at the other end of the slotted hole.
In the seventh embodiment, when the reciprocation driving unit is located at the first position, the pawl rotational pivot of the ratchet lever is located at the first position while the pin formed in the fixed part of the seatbelt retractor is located at one end of the slotted hole of the pawl. Therefore, the pawl is positioned apart from the ratchet gear, so that the ratchet gear can rotate freely and rotation of the spool is not prevented.
When the reciprocation driving unit is located at the second position, the pawl rotational pivot of the ratchet lever is located at the second position, so that the pawl is located at an engageable position with the ratchet gear. In this state, when the pin is located at the one end of the slotted hole, the pawl is engaged with the ratchet gear while when the pin is located at the other end of the slotted hole, the pawl is not engaged with the ratchet gear.
When the spool rotates in the withdrawing direction, the pawl rotates about the pawl rotational pivot so as to prevent the ratchet gear from rotation by abutting of the pin against the one end of the slotted hole. Therefore, rotation of the spool is prevented.
When the spool rotates in the retracting direction, the pawl is pushed by the ratchet gear so as to rotate about the pawl rotational pivot in the direction opposite to the aforementioned direction, so that the pin is positioned at the other end of the slotted hole. In this case, the pawl is not engaged with the ratchet gear and rotation of the ratchet gear is allowed.
As the eighth aspect of the invention, the seatbelt retractor in the seventh aspect further comprises an elastic body for urging the pawl in the rotational direction so as to bring the pawl into engagement with the ratchet gear.
In the eighth aspect, since the pawl is urged by the elastic body in the rotational direction so as to bring the pawl into engagement with the ratchet gear, when the reciprocation driving unit is located at the second position and the ratchet gear rotates in the withdrawing direction, the rotation can be prevented by secure engagement between the ratchet gear and the pawl.